JPH01233088A - Gas shield arc welding wire for high tensile strength steel - Google Patents

Abstract

PURPOSE:To improve toughness at cryogenic temp. by containing the specific ratio of C, Si, Mn, Ni, Al, Ti, P, S, N and the balance Fe component in a wire and if necessary, adding the prescribed quantities of Cr and Mo. CONSTITUTION:The component composition of the gas shield arc welding wire for high tensile strength steel is regulated to 0.01-0.08wt.% C, 0.10-0.30% Si, 0.80-2.00% Mn, 2.50-8.00% Ni, 0.010-0.030% Al, 0.02-0.10% Ti <=0.010% P and S, <=0.008% N and the balance Fe. Further, if necessary, <=2.0% Cr and <=1.0% Mo are added. As Si content is reduced to the lower limit and Al and Ti are added to suitable quantity, in the welded metal at the time of welding, the micro structure is made to fine and the toughness in the matrix can be improved. By this method, the toughness at the welded part in the temp. range of -80--100 deg.C is improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a gas-shielded arc welding wire using an Ar-C0□ mixed gas as a shielding gas, and more specifically, a high-tensile steel wire on a 60 kgf/- edge. This invention relates to a wire used in gas-shielded arc welding to obtain a deposited metal with particularly excellent low-temperature toughness.

(Prior Art) In recent years, large offshore structures have been constructed for the purpose of developing ocean energy resources. These structures include 60
kgf/- High tensile strength steel on the edging is often used, and since it is used in polar seas, it is required to have toughness in the low temperature range of about -80'C to -100°C. Furthermore, in the manufacture of these structures, there has been a desire for the development of gas-shielded arc welding wires (hereinafter referred to as wires) from the viewpoint of increasing the efficiency of welding.

Conventionally, low Ni containing about 3 to 4% Ni has been used for such applications.
system wire was used. However, it is difficult to ensure toughness in the low temperature range of -80°C to -100°C with these low-Ni wires, so a method to ensure toughness is to perform multilayer welding with low heat input. However, there were problems in that welding defects were likely to occur and welding efficiency was reduced, and improvements were needed.

As an example of solving the above problem,
In Publication No. 3, regarding II wire for gas-shielded arc welding of high-strength steel, the microstructure is insufficiently refined by conventional methods, and the acid-soluble and acid-insoluble components of /V and Ti are defined separately. An invention has been disclosed in which the microstructure is made finer and the toughness is improved by doing so. However, this method was insufficient to improve the toughness in the low temperature range of -80'C or less.

The reason for this is that the microstructure has not been sufficiently improved, and the toughness of the matrix itself needs to be improved in order to improve the toughness of weld metal in the low temperature range of -80°C to -100'C. I can think of something.

On the other hand, in order to perform gas shield arc welding in an oxidizing atmosphere using Ar-CO7 mixed gas as a shielding gas, a sclerotic acid agent such as Si or Mn is added to oxidize the weld metal. It is necessary to prevent blowholes from occurring due to this.

As an example of this, Japanese Unexamined Patent Publication No. 16072/1987 describes Si
is necessary as a deoxidizing element for the weld metal, and it is disclosed that at least 0.3% or more is required since deoxidizing becomes insufficient and a large number of blowholes occur if a small amount is used.

As described above, gas-shielded arc welding inevitably contains Si, and it is thought that Si dissolves in the ferrite and inhibits the toughness of the matrix itself, so that a sufficient effect of improving toughness cannot be obtained.

(Problems to be Solved by the Invention) As a result of various tests conducted by the present inventors regarding deoxidation and microstructure refinement in gas shielded arc welding,
In conventional wires containing about 0.3 to 0.4% St, the microstructure cannot be refined by simply adding AI and Ti, so we added appropriate amounts of AI and Ti in combination and reduced the amount of Si to the limit. I discovered that it is something that can only be achieved by forcing yourself to do it.

The present invention has achieved a finer microstructure of the weld metal by improving the deoxidation method in gas-shielded arc welding, and has significantly improved low-temperature toughness by reducing the amount of Si and improving the toughness of the matrix. The present invention provides an improved gas-shielded arc welding wire for high-strength steel.

(Means for solving problems) The gist of the invention is as follows.

(1) In weight%, C: 0.01-0.08%, SAl
:0, 10~0.30%, Mn: 0.80~2.00
%, M: 0.010-0.030%, TAL: 0.02
~0.10%, NAl: 2.50-8600%, P: 0
．． 0.010% or less, S: 0.010% or less, N: 0
．． 1. A gas-shielded arc welding wire for high-strength steel, characterized in that the wire contains 0.008% or less and the remainder is substantially iron.

(2) In weight%, c:o, o1~0°08%, SAl:
0.1.0-0.30%, Mn: 0.80-2.00
%, Al: 0, 010-0.030%, TAl: 0.0
2-0.10%, NAl: 2.50-8.00%, P
: 0.010% or less, S: o, oto% or less, N: 0
．． 008% or less, and one or two of Cr: 2.0% or less, Mo: 1.0% or less, and the remainder substantially consists of iron. Wire for shielded arc welding.

That is, the greatest feature of the present invention is that Si.

By performing complex deoxidation using ql, AI, and Ti,
The low-temperature toughness has been improved by making the most of the microstructure refinement effect of ALTi and reducing the amount of Si as much as possible to improve the toughness of the matrix itself.

In conventional gas shielded arc welding wire, Si
Since Mn-5 ilicate is used as the main deoxidizing agent, low melting point Mn-5 ilicate is generated during the deoxidation process, and this
Because it combines with the oxide of i to form large composite inclusions and reduces the number of nucleation sites that are effective for microstructure refinement, the microstructure cannot be refined sufficiently, resulting in a poor toughness improvement effect. The present invention was created by paying attention to the fact that the above was not obtained.

(Function) The reasons for limiting the component composition in the present invention will be described below.

C: 0.01-0.08% C is added in an appropriate amount to adjust the strength, but 0.01%
If it is less than 0.08, sufficient strength cannot be obtained;
If it exceeds 0.01%, the cracking resistance will decrease significantly.
~0.08%.

SAl: 0. IO ~ 0.30% Si is usually used as the main deoxidizer to prevent blowholes and obtain a sound weld.
Add 4% or more. However, a suitable amount of hel.

Addition of Ti in combination can supplement the deoxidizing ability of Si and suppress the generation of blowholes. FIG. 1 shows an example in which wires having two types of composition shown in Table 1 were studied using the welding conditions and groove shapes shown in Table 2 and FIG. In group B wires that do not contain AI or Ti, deoxidation is insufficient and blowholes occur when the Si content is less than 0.3%. On the other hand, in group A in which AI and Ti are added in combination, blowholes do not occur until the amount of Si is 0.1%, and deoxidation is improved by adding AI and Ti in combination.

Furthermore, if SiN exceeds 0.30%, the microstructure refinement effect of Al and Ti will be impaired, and furthermore, it will cause solid solution hardening of the matrix, which will significantly reduce the toughness. And so.

Mn: 0.80-2.00% Mn is effective in assisting deoxidation and improving the fluidity of molten metal, and is also effective in improving strength and toughness. However, if it is less than 0.80%, the fluidity of the molten metal will be insufficient and welding defects will easily occur, and if it exceeds 2.00%, the cracking resistance will be significantly impaired, so it is set at 0.80 to 2.00%.

P: 0.010% or less P not only dissolves in ferrite and impairs the toughness of the matrix, but if it exceeds 0.010%, it forms a low melting point compound with Ni, significantly embrittles grain boundaries and impairs durability. Since it reduces crackability, it is set to 0.010% or less.

s: o, o1o% or less S, like P, if it exceeds 0.010%, it forms a low melting point compound with Ni and significantly impairs cracking resistance, so 0.01
It was set to 0% or less.

A1: 0.010-0.030% It is a strong film acid agent, and is most effective in compensating for the decrease in deoxidizing power due to a decrease in 5ilJ, preventing oxidation of the weld metal, and obtaining a sound weld. If it is 0.05% or more, the integrity of the welded part can be maintained.

Further, in order to refine the microstructure and improve toughness together with Ti, further adjustment of the amount of the components is required.

Table 2 for the two groups of wires shown in Table 3;
Fig. 3 shows an example of the study using the welding conditions and groove shape shown in Fig. 2. In the C group wire with Si content of 0.2%,
It is clear that the low temperature toughness is significantly improved when the AI amount is in the range of 0.010% to 0.030%. or,
If it exceeds 0.03%! Oxidized proboscis increases dramatically,
Forms large complex oxides and reduces oxidation properties.

On the other hand, wires of group D with Si content of 0.4% are M
Toughness decreases in proportion to increase in amount. That is, it is clear that because the amount of Si is excessive, the effect of microstructure refinement by AI and Ti cannot be obtained, and the toughness of the matrix is reduced, so that low-temperature toughness is not improved.

Therefore, to! The amount was 0.010-0.030%.

TAl: 0.02 to 0.10% TI, along with AI, is a strong oxidizing agent that prevents the oxidation of the weld metal, and refines the microstructure of the weld metal by forming Ti oxides, which is effective in improving toughness. be.

In order to compensate for the deoxidation caused by a decrease in the amount of Si, the amount may be 0.01% or more, but if it is less than 0.02%, the effect of improving the toughness due to microstructure refinement cannot be obtained, and if it exceeds 0.10%, carbide 0.02 as it forms and significantly impairs the stiffness.
~0.10%.

Nt: 2.50-8.00% Ni is effective in improving the toughness of the weld metal matrix.
It is an indispensable component for improving rosacea at temperatures of about -80 to -100°C. However, if it is less than 2.50%, the effect of improving toughness is insufficient, and if it exceeds 8.00%, the cracking resistance will be significantly reduced, so it is set at 2.50 to 8.00%.

N: 0.008% or less N does not impair the integrity of the weld if it is 0.015% or less, but it tends to form nitrides with Af and Ti, so it is difficult to deoxidize and refine the microstructure. AI that contributes to T
As a result of decreasing the amount of i, the toughness is significantly lowered, so the upper limit was set at 0.008%.

P: 0.010% or less P not only dissolves in ferrite and impairs the toughness of the matrix, but if it exceeds 0.010%, it forms a low melting point compound with Ni, significantly embrittles grain boundaries and impairs durability. Since it reduces crackability, it is set to 0.010% or less.

S: 0.010% or less Like P, S exceeds o, o io%, forms a low melting point compound with Ni, and significantly impairs cracking resistance, so it should not be 0.
．． 0.010% or less.

In addition, Cr and Mo are used to improve the hardenability of weld metal and increase its strength and toughness.
If it exceeds 2.0%, the weld metal will be significantly hardened and the toughness and cracking resistance will decrease, so it was set at 2.0% or less.

In addition, if Mo exceeds 1.0%, Mo carbide will be generated, hardening the weld metal and significantly impairing the toughness, so Mo should be set at 1.0%.
The following was made.

Hereinafter, the present invention will be specifically explained with reference to Examples.

(Example 1) Using the wires shown in Table 4, welded joints were produced under the welding conditions and groove shapes shown in Table 5 and FIG. 4. Tensile test pieces and Charpy impact test pieces were taken from this welded joint, and mechanical tests were conducted. The results are shown in Table 6.

Also, if the absorbed energy at -101°C is 4.8 kg/m or more, it is considered to have good low-temperature toughness.

In Table 4, E1 to E4 are wires of the present invention, and F1
~F5 is a comparison wire that is outside the scope of the present invention.

Wires E1 to E4 in which the main alloy component content and the amounts of Si, AI, and Ti are within the limits of the present invention all obtain good low-temperature toughness.

On the other hand, in comparison wire F1, in which the Ni amount is below the range of the present invention and the amount exceeds the range of the present invention, the amount of Ni is excessive and the microstructure refinement effect cannot be obtained, and the amount of Ni is insufficient and the matrix is It has low lentiginous properties due to lack of lenticulence.

Comparative wire F2, in which the amount of C exceeds the range of the present invention and the amount of AI is below the range of the present invention, has an excessive amount of C and the weld metal is excessively hardened, and the microstructure refinement effect by IV cannot be obtained. Testability is low.

Comparative wire F3, in which the St content exceeds the range of the present invention and the Mn content is below the range of the present invention, has an AI characteristic of the present invention.
, the toughness was low because the effect of improving the toughness due to Ti composite addition was not obtained.

Comparison wire F whose P, S and N amounts exceed the range of the present invention
No. 4 has low toughness because low melting point compounds are produced and the amount of N is excessive.

In addition, comparison wire F5, in which the amount of Si and Ti exceeds the range of the present invention, does not have sufficient toughness because the toughness of the matrix is not improved and the amount of Ti is excessive, causing Ti carbide to precipitate and the weld metal to harden significantly. is not obtained.

As described above, it is clear that the wire of the present invention achieves a finer microstructure for the first time, and furthermore, the effect of reducing the amount of Si to the maximum and improving the toughness of the matrix is combined to improve the toughness. .

(Example 2) Welded joints were prepared using the 80 kgf/++j class wire shown in Table 7 under the welding conditions and groove shapes shown in Table 8 and FIG. 5. Tensile test pieces and Charpy impact test pieces were taken from this welded joint, and mechanical tests were conducted. The results are shown in Table 9.

Further, if the absorbed energy at -80°C is 4.8 kg/m or more, it is assumed that the material has good low temperature resistance.

In Table 7, G1-G4 are the wires of the present invention, and H1
~J(3 is a comparison wire outside the scope of the present invention).

The amounts of Si, IV, and Ti are within the limits of the present invention, and Cr,
Wires G1 and G4 of the present invention containing Mo, wire G2 containing only Cr, and wire G3 containing only Mo all exhibit good toughness.

However, in the comparison wire H1 in which Ni is below the range of the present invention and Mo content is above the range of the present invention, the toughness of the matrix is insufficient due to the insufficient Ni content, and the weld metal is hardened due to the excessive Mo content. Therefore, low-temperature toughness is insufficient.

Comparative wire H2, in which the amount of Si exceeds the range of the present invention and the amount of Cr exceeds the range of the present invention, has an excessive amount of Si, which reduces the tenacity of 7 trix, and an excessive amount of Cr, which causes the weld metal to harden significantly. Therefore, low-temperature toughness is insufficient.

In addition, in comparison wire H3, in which the amounts of Au and Ti are lower than the range of the present invention, and the amount of N is further outside the limits of the present invention, the effect of improving toughness due to microstructure refinement cannot be obtained, resulting in insufficient low-temperature toughness. .

As described above, it is clear that the wire of the present invention achieves a finer microstructure for the first time, and furthermore, the effect of reducing the amount of Si to the maximum and improving the toughness of the matrix is combined to improve the toughness. .

(Effects of the invention) As shown above, the wire of the present invention has a -80
Toughness can be improved in a low temperature range of about -100°C, and good low-temperature toughness can be ensured without reducing welding efficiency.

Therefore, it is possible to improve the quality of welded parts and welding efficiency in welding of structures such as offshore structures that use high tensile strength steel of 60 kgf/mm2 class or higher and are used under severe conditions.

[Brief explanation of the drawing]

Figure 1 shows the effects of Si, /V, and Ti on the integrity of welds.
Figure 2 is a front view showing the groove shape used in Figure 1, Figure 3 is the effect of Si on the toughness of weld metal,
A/, Figures 4 and 5 showing the influence of the amount of Ti are front views showing the groove shapes used in the examples of the present invention. 0 θ2 θ4 0.6 0.
8 10Si amount (bottom 2) Fig. 2 Fig. 3 0 0.02 004 0θ6
0.08 0. /θAA amount (wt
%)

Claims (2)

[Claims] (1) In weight%, C: 0.01-0.08%, Si: 0
．． 10-0.30%, Mn: 0.80-2.00%, Ni: 2.50-8.00%, Al: 0.010-0.030%, Ti: 0.02-0.10% , P: 0.010% or less, S: 0.010% or less, N: 0.008% or less, and the remainder is substantially iron. Wire for. (2) In weight%, C: 0.01-0.08%, Si: 0
．． 10-0.30%, Mn: 0.80-2.00%, Ni: 2.50-8.00%, Al: 0.010-0.030%, Ti: 0.02-0.10% , P: 0.010% or less, S: 0.010% or less, N: 0.008% or less, Cr: 2.0% or less, Mo: 1.0% or less, one or two of the following. A wire for gas-shielded arc welding for high-strength steel, characterized in that it contains seeds and the remainder consists essentially of iron.